Embodiments of the present invention relate to high-power electric motor rotors intended to operate at particularly high rotation speeds. In particular, embodiments of the present invention apply to asynchronous motors able to operate at high peripheral speeds typically from 100 m·s−1, motors especially intended for gas and oil applications, whether on land, in sea, or even underwater.
The peripheral speed is the calculated tangential velocity at the outer diameter of the rotating rotor.
High-power electric motors able to operate at high rotation speeds have numerous applications. Manufacturing of motors meeting the growing requirements in terms of power and speed imposes new stresses, particularly mechanical, in the rotor of said motors. Patent documents EP 0 608 675 A1 and U.S. Pat. No. 5,512,792 describe particularly effective embodiments of rotors for asynchronous electric motors, operating at high power and speed. A rotor is thus described whose bars forming the squirrel cage can freely expand, thus mitigating effects due to thermal imbalances.
Nevertheless, in order to further increase the power received by this type of motor, increasing the diameter of the bars forming the squirrel cage proves to be necessary to avoid excessive heating of the latter. However, on the basis of the examples described in the patents mentioned above, increasing the sections of said bars results in reduction of distances between these same bars. This solution thus proves to be less satisfactory because the reduction of spacing between each bar introduced new magnetic and mechanical stresses, which ultimately leads to weakening of the rotor.
The patent document FR 2 950 751 proposes a rotor able to be integrated in an electric motor with improved characteristics in terms of supported power and peripheral rotation speed, particularly by its capacity to carry a larger electric power through the squirrel cage of the rotor. To do this, the rotor comprises several electrical conductors, each conductor being formed by assembly of a main bar and a secondary bar respectively having a substantially circular section and passing through the magnetic body of the rotor through a notch. The shape and arrangement of each notch are defined so as to ensure a contact between the main bar and the secondary bar sufficient to allow passage of electric current when the rotor is rotating.
However, such an assembly leads to difficulties in implementation. In particular, while the operating temperature is not stabilized, differential deformations between the main bar and the secondary bar lead, on one hand, to the existence of an unbalance and, on the other hand, to poor electrical contact between the main bar and the secondary bar.